The maneuver involved a 17,000-tonne structure, the heaviest ever lifted in the world. The P-55 is the largest semi-submersible platform built in Brazil and is to operate in the Campos Basin (state of Rio de Janeiro)
Petrobras completed the deck mating operation for the P-55 semi-submersible platform at the Rio Grande Naval Hub (state of Rio Grande do Sul). This operation involves coupling the platform’s topside deckbox with the hull. The deck mating procedure entailed lifting the deckbox, a technique never used before in Brazil, and represented a record achievement in terms of the weight of the structure and to the height to which it was lifted.
The lifting system consisted of 12 towers connected to 24 hydraulic jacks each with a capacity of 900 tonnes. It was designed to raise the deckbox to a height of 47.2 meters above the bottom of the shipyard’s dry dock. Twenty-four sets of 54 steel wire ropes were used to lift the structure. Each wire rope was 18-mm in diameter and 60 meters long, giving a total length of around 77 kilometers.
The modules will be installed and the system integrated in the coming months. After this stage has been completed, the P-55 will be transported to the Campos Basin’s Roncador oilfield, off the coast of Rio de Janeiro, and is expected to start operating in September 2013. At full capacity, the P-55 is capable of producing up to 180,000 barrels of oil and six million m3 of natural gas per day.
Petrobras’ CEO Maria das Graças Silva Foster was at the Rio Grande Naval Hub during the deck mating operation, together with the company’s directors. “The people of Rio Grande do Sul and all Brazilians have good reason to be proud of this achievement. The sheer scale of the operation is amazing. This is the first ever platform built at the Rio Grande Naval Hub and largest semi-submersible platform ever built in Brazil,” she said. Maria das Graças also highlighted the uniqueness of the operation and the potential of the naval hub. “This is the first time a deck mating operation, coupling the modules and hull, has ever been done using this technique. The deckbox, weighing 17,000 tonnes, was raised over 40 meters and lowered onto the hull. The usual procedure is to lower the hull. The P-55 and the eight replicant FPSOs to be built here will be Brazilian and international benchmarks.”
Replicant FPSOs are a new generation of platforms designed to simplify projects and standardize equipment. Serial production of identical hulls will not only make the construction process faster and allow for economies of scale, but also optimize costs.
The P-55′s hull was developed by the Petrobras Research Center (Cenpes). It is the outcome of several years’ engineering research and development in partnership with Brazilian universities and based on entirely Brazilian technology, representing another milestone for the oil industry in Brazil.
The deck mating procedure began on June 25, when the deckbox was raised for the first time to a height of 20 cm for testing and final weighing. Lifting was continued on June 27. On June 28, the deckbox reached 15.4 meters above the bottom of the dock. At the same time, the keel blocks were rearranged and fenders erected inside the dock, procedures which were completed on June 30.
The water collection pipeline valves were opened and the flooding process started on the same day. Some 642 million liters of water were needed to fill the dock to a depth of 13.8 meters. Once the flooding had been completed, the floating gate (caisson) was opened (July 2) to float the hull of the P-55 into the dock and then closed. Next day, the water inside the dock was drained to a level of 7.2 m.
The deckbox was lifted to its maximum height of 47.6 meters on July 5 and 6 and the hull aligned underneath it. On July 7, final adjustments were made to the hull position under the deckbox, which was then lowered onto it to complete the deck mating operation. The next step will be to drain the dock until the hull/deckbox assembly is fully supported on the concrete keel blocks.
Source: Petrobras, July 11, 2012